Effect of Arched Leaflets and Stent Profile on the Hemodynamics of Tri-Leaflet Flexible Polymeric Heart Valves

Abstract

Polymeric heart valves (PHV) can be engineered to serve as alternatives for existing prosthetic valves due to higher durability and hemodynamics similar to bioprosthetic valves. The purpose of this study is to evaluate the effect of geometry on PHVs coaptation and hemodynamic performance. The two geometric factors considered are stent profile and leaflet arch length, which were varied across six valve configurations. Three models were created with height to diameter ratio of 0.6, 0.7, and 0.88. The other three models were designed by altering arch height to stent diameter ratio, to be 0, 0.081, and 0.116. Particle image velocimetry experiments were conducted on each PHV to characterize velocity, vorticity, turbulent characteristics, effective orifice area, and regurgitant fraction. This study revealed that the presence of arches as well as higher stent profile reduced regurgitant flow down to 5%, while peak systole downstream velocity reduced to 58% and Reynolds Shear Stress values reduced 40%. Further, earlier reattachment of the forward flow jet was observed in PHVs with leaflet arches. These findings indicate that although both geometric factors help diminish the commissural gap during diastole, leaflet arches induce a larger jet opening, yielding to earlier flow reattachment and lower energy dissipation.

Keywords: Commissure coaptation; Fluid mechanics; Particle image velocimetry; Polymeric heart valve; Prosthetic heart valve; Reynolds shear stress; Turbulent kinetic energy.

Figure 1

Assembling leaflet and stents for manufacturing each heart valve (left), Top view of each six HVs: (a)LPNA, (b) LPSA, (c) LPLA, (d) MPNA, (e) MPSA, (f) HPNA.

Figure 2

Schematic of left heart flow loop, used to impose physiological pressures and flow rates across the aortic valve.

Figure 3

Flow and pressure curved obtained from LabVIEW data for each HV. (a) Flow and pressure for MPSA valve model. (b) Flow and pressure curves for LPNA valve model.

Figure 4

Regurgitantflow fraction during each cardiac cycle, error bars are standard deviation for 10 cycles. (a) Reverse flow fraction for HVs without arch and varying length. (b) Reverse flow fraction for short profile HVs with varying arch length.

Figure 5

Snapshots of HV models without arch at four phases during the cardiac cycles.

Figure 6

Snapshots of HV models with arch at four phases during the cardiac cycles.

Figure 7

Effect of stent height on left: ensemble averaged velocity vectors and vorticity contours; and right: normalized Reynolds Shear Stress contours, at selected time points during the cardiac cycle.

Figure 8

Effect of leaflet arch on left: Ensemble averaged velocity vectors and vorticity contours; and right: Normalized Reynolds Shear Stress contours, at selected time points during the cardiac cycle.

Figure 9

Schematic drawing of the effect of left: stent profile; and right: leaflet arch, on the hemodynamics of the prosthetic aortic heart valve.